Carrier 33ZCVAVTRM Specifications download pdf (Page 154)

Table 7 - Available Cooling Stages

* If conditions are suitable for economizer operation.

Dehumidification – The PremierLink controller will provide

occupied and unoccupied dehumidification control when

AUXOUT = 5 in the CONFIG table and is installed on HVAC

units that are equipped with additional controls and accessories

to accomplish this function. This function also requires a space

relative humidity sensor be installed on the OAQ/IRH input.

When in the occupied mode and the indoor relative humidi-

ty is greater then the Occupied High Humidity set point, then

the H3_EX_RV output point will be energized. When in the

unoccupied mode and indoor relative humidity is greater then

the Unoccupied High Humidity set point, then the H3_EX_RV

output point and supply fan output will be energized. There is a

fixed 5% hysteresis that the indoor relative humidity must drop

below the active set point to end the dehumidification mode

and deenergize the H3_EX_RV output. If the Premierlink con-

troller is in the unoccupied mode, then the fan relay will deen-

ergize if there is no other mode requiring to the fan to be on.

This function will not energize mechanical cooling as a result

of the indoor relative humidity exceeding either set point.

A high humidity alarm will be generated if the indoor rela-

tive humidity exceeds the high humidity set point by the

amount configured in the Control Humidity Hysteresis in the

ALARMS table for 20 minutes. The alarm will return to nor-

mal when the indoor relative humidity drops 3% below the ac-

tive humidity set point.

Economizer

— The economizer dampers are used to provide

free cooling and indoor air quality if optional CO

sensor is in-

stalled and when the outside conditions are suitable. Tempera-

ture control is accomplished by controlling the SAT to a certain

level determined by the Economizer PID Loop by calculating a

submaster reference (ECONSR) value. This algorithm will cal-

culate the submaster reference temperature (ECONSR) based

on OAT and enthalpy conditions and cooling requirements.

The ECONSR value is then passed to the Economizer Submas-

ter Loop, which will modulate dampers to maintain SAT at

ECONSR level.

The following conditions are required to determine if econ-

omizer cooling is possible:

• Indoor fan has been on for at least 30 seconds

• Enthalpy is low

• SAT reading is available

• OAT reading is available

• SPT reading is available

•OAT ≤ SPT

• OAT < OATMAX (OATMAX default is 75 F)

• Economizer position is NOT forced

If any of the above conditions are not met, the ECONSR

will be set to its MAX limit of 120 F and the damper will go to

its configured minimum position. The minimum damper posi-

tion can be overridden by the IAQ routine described later in

this section.

The calculation for ECONSR is as follows:

ECONSR = PID function on (set point – SPT), where:

set point = ((OCSP+STO) + (OHSP+STO))/2 when NTLO

(Unoccupied Free Cool OAT Lockout) < OAT < 68 F

setpoint = (OCSP+STO) – 1 when OAT ≤ NTLO

setpoint = (OHSP+STO) + 1 when OAT ≥ 68 F

The actual damper position (ECONPOS) is the result of the

following calculation. Values represented in the right side of

the equation can be found in the SERVICE configuration table

descriptions in this manual. Note that that the OAT is taken into

consideration to avoid large changes in damper position when

the OAT is cold:

ECONPOS = SubGain x (ECONSR–SAT) + CTRVAL

where SubGain = (OAT – TEMPBAND) / (ESG + 1)

If the OAT < DXLOCK (DX Cool Lockout set point) then

the damper will be modulated to maintain the SAT at the

ECONSR value.

If the OAT is between DXLOCK and 68 F (DXLOCK <

OAT < 68 F) and additional cooling is required, the economizer

will close the to minimum position for three minutes, the

economizer integrator will then be reset to 0 and begin modu-

lating to maintain the SASP after the stage has been energized

for about 90 seconds. This will allow the economizer to calcu-

late a new ECONSR that takes into account the cooling effect

that has just been turned on and not return to the value require

before the cooling was added. This will prevent the economiz-

er from causing premature off cycles of compressors while

maintaining the low SAT temperature set point for the number

of stages active. In addition to preventing compressor short cy-

cling, by using return air across the evaporator coil just after the

compressor has started allows for increased refrigerant flow

rates providing for better oil return of any oil washed out dur-

ing compressor start-up.

If the OAT > 68 F and OAT < SPT and the number of DX

stages requested is > 0 by the staging algorithm, then ECONSR

is set to its minimum value 48 F and the damper will go to

100% open.

If the Auxiliary Relay is configured for exhaust fan (AUX-

OUT = 1) in the CONFIG configuration table and Continuous

Power Exhaust (MODPE) is Enable in the SERVICE configu-

ration table, then the AUXO output (HS3) will be energized

whenever the PremierLink controller is in the occupied mode.

If the MODPE is disabled then AUXO output will be energized

based on the Power Exhaust Setpoint (PES) in the SETPOINT

table.

Heating

— The heat stages are controlled by the Heating Con-

trol Loop, which is used to calculate the desired SAT needed to

satisfy the space. It will compare the SPT to the Occupied Heat

Setpoint (OHSP) + the T56 slider offset (STO) when occupied

and the Unoccupied Heat Setpoint (UHSP – Unoccupied Heat-

ing Deadband) if unoccupied to calculate a Staged Heat Sub-

master Reference (SHSR). The heat staging algorithm com-

pares the SHSR to the actual SAT to calculate the required

number of heating stages to satisfy the load. This loop runs ev-

ery 40 seconds. The following conditions must be met in order

for this algorithm to run:

• Indoor fan has been ON for at least 30 seconds.

• Cool mode is not active and the time guard between modes

equals zero.

• Mode is occupied or the Temperature Compensated Start or

Heat mode is active.

• SPT reading is available and < (OHSP + STO).

• If it is unoccupied and the SPT < (UHSP – Unoccupied

Heating Deadband). The indoor fan will be turn on by the

staging algorithm.

When all of the above conditions are met, the SHSR is cal-

culated and up to 3 stages of heat will turned on and off to satis-

fy to maintain the SAT = SHSR. If any of the above conditions

are not met, the SHSR is set to its minimum value of 35 F.

The Staged Heat Submaster Reference (SHSR) is calculated

as follows:

SHSR = Heating PID function on (error) where

error = (OHSP + STO) - Space Temperature

The Maximum SHSR is determined by the SATHI configu-

ration. If the supply-air temperature exceeds the SATHI config-

uration value, then the heat stages will turn off. Heat staging

Number of Stages 0

(Economizer*)

Compressor 1 Off Off On On

Compressor 2 Off Off Off On

1 2 ... 149 150 151 152 153 154 155 156 157 158 159 ... 315 316

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Carrier 33ZCVAVTRM Specifications Page 154

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